The present invention relates to a digital magnetic reproducing apparatus and a digital magnetic recording/reproducing apparatus using, for example, a magnetic disk as a recording medium.
In the field of digital magnetic recording, there is currently in progress the introduction of a signal processing method which ensures a satisfactory precision of code identification even in a high linear density area with a high-sensitivity magnetoresistance effect head (hereinafter referred to as an MR head) capable of achieving an adequate signal-to-noise ratio even in a narrow track, i.e., a processing method termed PRML (Partial Response Maximum Likelihood) which is a combination of partial response equalization and maximum likelihood decoding.
However, in realization of high surface density recording by the combination mentioned above, there exists the problem in that a data error rate in a channel is deteriorated due to the harmful influence of nonlinear distortion peculiar to an MR head. Such deterioration results from the fact that the PRML method is premised, in principle, on a linear recording/reproducing channel.